The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Nonvolatile optical data storage systems include compact disc (CD) systems, digital versatile disc (DVD) systems and, more recently, Blu-ray Disc (BD) and Blu-ray Disc XL (BDXL) systems. An optical data storage control system generally includes a buffer that stores read data, write data and/or volatile control code that is associated with the control of the system. Flash memory can also be used for critical data such as data relating to write formats and/or other nonvolatile control code. The optical data storage control system may also include a microprocessor of a computing system such as a server, a personal computer, a personal digital assistant (PDA), etc., or of a consumer electronics device such as a gaming system, etc., to allow the microprocessor to store data to and read data from the optical disc. The microprocessor may perform data and/or control processing that is related to the operation of the system. The microprocessor also performs decoding of copy protection and/or compression/decompression as needed. An input/output interface receives data to be written to the optical disc and transmits data read from the optical disc. A control module communicates with the input/output interface and with a spindle/feed motor (FM) driver and/or a read/write channel (RWC) device. The control module coordinates control of the spindle/FM driver, an actuator controller, the read/write channel device and the microprocessor and data input/output via the interface. Additionally, the RWC device may be coupled to the actuator controller. The RWC device may include a read channel device.
An optical data storage assembly includes an optical platter or disc that stores data optically. During write operations, the read/write channel module encodes the data to be written by an optical read/write device, such as an optical pick-up unit (OPU). During read operations, the read/write channel module converts an analog output of the OPU device to a digital signal. The converted signal is then detected and decoded by known techniques to recover the data that was written on the optical disc.
The optical disc is rotated by a spindle motor at a controlled and/or variable speed during the read/write operations. The OPU device moves relative to the disc to read and/or write data to/from the disc. The OPU may be attached to a sled, and a motor may be used to control position the sled over the optical disc.
The OPU device typically includes a laser and an optical sensor. For read/write and read only systems, the laser is directed at tracks on the disc that contain lands and pits during read operations. The optical sensor senses reflections caused by the lands/pits. The spindle/FM driver controls the spindle motor, which controllably rotates the disc. The spindle/FM driver also generates control signals that position the feed motor, for example using a voice coil actuator, a stepper motor or any other suitable actuator. The feed motor typically moves the OPU device radially relative to the disc. A laser driver generates a laser drive signal based on an output of the read/write channel module.
Portions of the optical data storage system may be implemented by one or more integrated circuits (IC) or chips. For example, the microprocessor and the control module may be implemented by a single chip. The spindle/FM driver and/or the read/write channel module may also be implemented by the same chip as the microprocessor, the control module and/or by additional chips.
The optical disc stores digitally encoded data as a series of marks separated by small spaces. The OPU reads the marks to recover the data encoded in the marks.
Recovering and matching the timing of the signal from the optical disc is one area in which errors in reading and decoding data may occur, particularly with high frequency modulated (HFM) data.